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Lower limit on decoherence introduced by entangling two spatially-separated qubits

A. J. Fisher
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Abstract

It is shown that a generalization of the fluctuation-dissipation theorem places an upper bound on the figure of merit for any quantum gate designed to entangle spatially-separated qubits. The bound depends solely on the spectral properties of the environment. The bound applies even to systems performing a quantum computation within a decoherence-free subspace, but might be optimized by the use of non-equilibrium squeezed states of the environment, or by using an environment system constructed to have response confined to certain frequencies.

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A. J. Fisher. 2002-11-29. Lower limit on decoherence introduced by entangling two spatially-separated qubits. https://arxiv.org/abs/quant-ph/0211200

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